The present invention relates generally to tools for applying fasteners to a workpiece and more particularly to such tools where guiding of the fastener to the workpiece is required, where a controlled depth of drive is advantageous and where multiple impacts may be advantageous.
Many types of tools exist in the prior art which can be used to fasten articles to a workpiece using suitable fasteners. There are, of course, many articles which can be commonly desired to be fastened to the workpiece. One of those articles is electrical cable. One particular type of electrical cable which is commonly stapled to the wooden frame construction of a dwelling or other building is Type NM cable, also known as Romex. Type NM cable is extensively used in the wood frame building construction.
Several types of fasteners have been used to fasten such an electrical cable to the wood frame construction. One of these fasteners is a staple consisting of a plastic strap with a nail punched through the plastic strap on either side of the cable. Another is a metal staple formed with a substantially U-shape. Both of these common staples suffer from the same disadvantages. Both are loose piece fasteners. That is, the staples are individual and must be individually selected and utilized. Another disadvantage for these common staples is that they require multiple of blows from a hammer. This requires essentially a manual operation hammering the staples in place around the electrical cable.
There do exist some staplers suitable for this use; however, these staplers usually suffer from the problem of being very large and cumbersome due to the power required to drive a staple with one blow. And they suffer the further disadvantage in that the material utilized for the staples is limited due to the force required to drive the staple with a single blow. The staple must be strong enough to survive the impact causing it to be driven with one blow. A further disadvantage is encountered in that with vinyl sheathed electrical cable it is desirable to control the drive depth of the stapler. The staple must be driven far enough to allow it to securely hold the electrical cable but must not be driven too far causing a cutting of the vinyl sheath or electrical insulation of the wires. With a stapling tool, this is a particular problem since these tools are generally large and cumbersome and it is difficult to see how far the staple is being driven. This is also a problem with multiple impact staplers since the number of impacts required depends upon the thickness of the article or articles being fastened, the particular staple being used, the resistance of the workpiece to the staple and the possible deflection of the workpiece away from the tool.